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From Cedric Pinson, this commit contains the following change:
* Change ref_ptr to observer_ptr to avoid cross reference and leak in Skinning
* Set invalidate to true to re run the check visitor in Skeleton
* Shallow copy Sampler in channel copy constructor
* Add accessor in VertexInfluence?
* Remove dead code in Timeline.cpp
* Dont force linking in Bone::UpdateBone?, the decision is done by the user or the manager
* Add offset in timeline stats to display each manager on the screen
* Add a flag in animation manager base to enable or not automatic link when modifying the manager